Telephone-exchange apparatus



(No Model.)

J. A. SEBLY.

TELEPHONE EXCHANGE APPARATUS.

No. 476,826. PatentedJune 14, 1892.

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,UN ATES PATENT OFFICE.

JOHN A. SEELY, OF BROOKLYN, NEIV YORK, ASSIGNOR TO THE WESTERN ELECTRICCOMPANY, OF CHICAGO, ILLINOIS.

TELEPHONE-EXCHANGE APPARATUS.

SPECIFICATION forming part of Letters Patent No. 476,826, dated June 14,1892.

Serial No. 331.495. (No model.)

To. all whom it may concern.-

Be it known that I, JOHN A. SEELY, a citizen of the United States,residing at Brooklyn, in the county of Kings and State of New York,

have invented a certain new and useful Improvement in Telephone-ExchangeApparatus, (Case No. 8,) of which the following is a full, clear,concise, and exact description,reference being had to the accompanyingdrawing, forming a part of this specification.

My in ven tion relates to telephone-exchange apparatus; and its objectis to provide ready means of sending current over metallic circuits whensaid metallic circuits are not provided with any ground connection atthe subscribers stations thereon.

My invention consists in metallic circuits each connected with two ormore switchboards at the central office and loop-plugs anddoublestranded cords at each of the switchboards, one of said strandsbeing grounded, and a source of electric current and signal-keys soarranged that the operator at the central office may send current overany metallic'circuit telephone-line with which connection has been madeby depressing the appropriate generator-key, thereby completing thecircuit from ground through the generator to the strand of the cordextending to the tip of the loop-plug thereof, and thence over the metallic circuit and back to the strand of the cord connected with the sleeveof said plug, and thence to ground through the branch which contains theretardation-coil, this branch containing the retardation-coil beingutilized for testing purposes, as heretofore.

My invention will be readily understood by reference to the accompanyingdrawing, in which I have shown three metallic-circuit subscribersstations connected each with three different switchboards at the centraloffice, together with an operators outfit at each of two of said boards,the subscribers outfit being shown in detail at one only of thestations. Telephone-line a extends in two branches or limbs from station1 to the central office, one limb I) being connected through the springsand contacts of each of the switches c d e of the different switchboardsand through the individual annnnciatorf on the first board, while theother limb g of said circuit a is connected with the test-pieces of eachof said switches a d c and with the other side of said individualannunciatorf.

The metallic circuits of stations 2 and 3 are provided with similarconnections, thus when the telephone is on the switch at any station thegenerator of said station is in a metallic circuit, including theindividual annunciator of the line at the central office.

At switchboard 3 I have shown the circuits of stations 3 and 1 loopedtogether by a'pair of loop-plugs 7a 'a', and the double-stranded cordsconnecting therewith. The strand in of said cords may be considered asconnecting with the tips of the plugs and the strand I as connected withthe sleeves thereof. The strand Z is provided with a branch on through aretardation-coil and test-battery to ground, this battery being designedto throw current onto a line when a loop-plug is inserted in a switchthereof, so as to bring the line into electrical condition to indicatethe busy test.

In the other strand 7c of the cord I place ringing-keys n 0, adapted toopen the circuit of said strand and connect the generator therewith ineither direction.

At board 1 I have shown the test-plug p applied to the switch of theline of subscribers station 2, upon board 1, as in the act of test- Soing said line. This is the ordinary test here tofore used and wellunderstood.

I will now describe the manner of calling the central office andcompleting the connections at the central office between the callingline and the line of the subscriber called for. Suppose subscriber atstation 3 wishes connection with subscriber of station 1. I have notdeemed it necessary to describe in detail the apparatus at station 3,since it is of the 0 same construction as that shown at station 1, andwhen the telephone is on the switch the generator will be included inthe circuit of station 3. The subscriber at station 3 will thereforeturn his generator and operate his 5 individual annunciator upon board 3included in his metallic circuit. The operator will thereupon insertloop-plug h of her pair into the switch of the line of station 3, andbringing her telephone into circuit will learn what IOO subscriber iswanted. In this instance it will be the line of station 1. This line awill be tested first in the usual manner and then the plug 1' will beinserted therein, and then by means of signal-key 0 current will be sentover metallic circuit a, and this circuit may be traced from the groundthrough the generator at the central office to the said callingkey 0,and thence over a strand of the cord to the tip of plug 6, and thenceover limb b of circuit a, through station 1, and back over the limb g tothe sleeve of plug t', and thence to the strand connecting the sleevesofthe plugs, this strand being connected with the grounded branch,including the retardationooil, and thus the operator is enabled tosignal the subscriber over a circuit formed by grounding one limb of hiscircuit through the generator and the other limb through the branch on.When the telephone at station 1 is on the telephone-switch, the bellwill be included in circuit, and when key 0 is thus depressed thesubscriber at station 1 will benotified of the call. In case theoperator desires to signal station 3, she simply depresses key it, whichthus brings the generator into a circuit which is completed through thestrand 70 to the tip of plug h and thence over the metallic circuit ofstation 3 and back to the sleeve of plug h, and thence to ground throughthe branch containing the retardation-coil. When the subscriber isthrough talking, either by hanging up his telephone and turning hisgenerator may signal to clear out.

Having thus described my invention, I claim as new and desire to secureby Letters Patent' 1. The combination, with a metallic circuit,including a subscribers station and connected with switches distributedon different switchboards, of a loop-plug adapted to be inserted in oneof the switches of said line, said loopplug being provided with twostrands, one of said strands being provided with a permanent groundconnection through a retardation-coil and the other strand beingprovided with a key, and a source of electricity in a ground branch withwhich said key is adapted to be connected, substantially as and for thepurpose specified.

2. Two telephone-lines looped together in metallic circuit through thesubscribers station and a pair of loop-plugs and flexible cords foreffecting this looping together, one of the strands of said cords beingprovided with a branch to ground through a rctarda tion-coil and theother strand being provided with two calling-keys, in combination with asource of electricity in a ground branch with which said keys areadapted to be connected, whereby current may be sent over either of saidtelephone-lines through the subscribers station by operating theappropriate key, the circuit thus formed in either case being fromground at the central office through the source of electricity to thekey and thence to one strand of a cord and thence over the metalliccircuit and back to the other strand of the cord and thence through thebranch containin g the retardation-coil to ground.

In witness whereof I hereunto subscribe m y name this 15th day ofNovember, A. D. 1889.

JOHN A. SEELY.

WVitnesses:

J. MILTON FERRY, W. H. EARNST.

